The invention provides a device for separating and measuring air in high-pressure engine oil. The device comprises a separation chamber (1), a blade (2), a gas storage chamber (3), a screw (4), a venting chamber (5), a pressure-limiting venting valve (6), a diversion partition plate (7), and a measuring chamber (8). When air is separated, the venting chamber (5) is installed on the uppermost portion of the gas storage chamber (3); when the pressure applied to venting by engine oil is larger than a spring force, the venting valve is pushed away and gas and some engine oil in the gas storage chamber (3) is exhausted through a venting hole. When air is measured, the venting chamber (5) and the pressure-limiting venting valve (6) inside the venting chamber are taken down and the measuring chamber (8) is used for replacing the venting chamber (5); and scales are marked on the upper part in the measuring chamber (8) to read the gas volume. A deflating valve (9) is installed on the uppermostpart of the measuring chamber and is used for exhausting gas in the measuring chamber (8). Therefore, air inside the high-pressure engine oil can be separated and the air content of the engine oil isreduced, so that the fault occurrence in the engine lubrication system is reduced; and the air content of the high-pressure engine oil of the engine can be measured conveniently. Moreover, the devicehas advantages of simple structure and low cost.